import java.util.ArrayDeque;

class MyQueueUse {

    public ArrayDeque<Integer> s1;
    public ArrayDeque<Integer> s2;
    public MyQueueUse() {
        s1=new ArrayDeque<>();
        s2=new ArrayDeque<>();
    }
    
    public void push(int x) {
        s1.push(x);
    }
    
    public int pop() {
        if (empty()){
            return -1;
        }
        if (s2.isEmpty()){
            while (!s1.isEmpty()){
                s2.push(s1.pop());
            }

        }
        return s2.pop();
    }
    
    public int peek() {
        if (empty()){
            return -1;
        }
        if (s2.isEmpty()){
            while (!s1.isEmpty()){
                s2.push(s1.pop());
            }

        }
        return s2.peek();
    }
    
    public boolean empty() {
        return s1.isEmpty()&&s2.isEmpty();
    }
}